On Tue, Jul 12, 2011 at 09:48:53AM +0800, Felix Fietkau wrote:
> For unicast the hardware sometimes reports MIC errors even though the
> frame that it received actually contains a valid MIC - on some chips this
> can happen frequently enough to trigger TKIP countermeasures.
> Fix this issue by not reporting MIC errors for unicast frames with a
> valid key, letting mac80211 validate the MIC instead.
>
> Additionally, strip the MIC for all frames that the hardware considers
> valid to avoid wasting CPU cycles re-validating it.
>
> Signed-off-by: Felix Fietkau <nbd@xxxxxxxxxxx>
> ---
> drivers/net/wireless/ath/ath9k/recv.c | 44 +++++++++++++++++---------------
> 1 files changed, 23 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
> index 80bb04f..3d9359a 100644
> --- a/drivers/net/wireless/ath/ath9k/recv.c
> +++ b/drivers/net/wireless/ath/ath9k/recv.c
> @@ -814,16 +814,19 @@ static bool ath9k_rx_accept(struct ath_common *common,
> struct ath_rx_status *rx_stats,
> bool *decrypt_error)
> {
> -#define is_mc_or_valid_tkip_keyix ((is_mc || \
> - (rx_stats->rs_keyix != ATH9K_RXKEYIX_INVALID && \
> - test_bit(rx_stats->rs_keyix, common->tkip_keymap))))
> -
> + bool is_mc, is_valid_tkip, strip_mic, mic_error = false;
> struct ath_hw *ah = common->ah;
> __le16 fc;
> u8 rx_status_len = ah->caps.rx_status_len;
>
> fc = hdr->frame_control;
>
> + is_mc = !!is_multicast_ether_addr(hdr->addr1);
> + is_valid_tkip = rx_stats->rs_keyix != ATH9K_RXKEYIX_INVALID &&
> + test_bit(rx_stats->rs_keyix, common->tkip_keymap);
> + strip_mic = is_valid_tkip && !(rx_stats->rs_status &
> + (ATH9K_RXERR_DECRYPT | ATH9K_RXERR_CRC | ATH9K_RXERR_MIC));
> +
[...]
> if (!rx_stats->rs_datalen)
> return false;
> /*
> @@ -850,25 +853,9 @@ static bool ath9k_rx_accept(struct ath_common *common,
> if (rx_stats->rs_status & ATH9K_RXERR_PHY)
> return false;
>
> - if (rx_stats->rs_status & ATH9K_RXERR_DECRYPT) {
> + if (rx_stats->rs_status & ATH9K_RXERR_DECRYPT)
> *decrypt_error = true;
> - } else if (rx_stats->rs_status & ATH9K_RXERR_MIC) {
> - bool is_mc;
> - /*
> - * The MIC error bit is only valid if the frame
> - * is not a control frame or fragment, and it was
> - * decrypted using a valid TKIP key.
> - */
> - is_mc = !!is_multicast_ether_addr(hdr->addr1);
>
> - if (!ieee80211_is_ctl(fc) &&
> - !ieee80211_has_morefrags(fc) &&
> - !(le16_to_cpu(hdr->seq_ctrl) & IEEE80211_SCTL_FRAG) &&
How are we going to handle the above conditions?
> - is_mc_or_valid_tkip_keyix)
> - rxs->flag |= RX_FLAG_MMIC_ERROR;
> - else
> - rx_stats->rs_status &= ~ATH9K_RXERR_MIC;
> - }
> /*
> * Reject error frames with the exception of
> * decryption and MIC failures. For monitor mode,
> @@ -886,6 +873,18 @@ static bool ath9k_rx_accept(struct ath_common *common,
> }
> }
> }
> +
> + /*
> + * For unicast frames the MIC error bit can have false positives,
> + * so all MIC error reports need to be validated in software.
> + * False negatives are not common, so skip software verification
> + * if the hardware considers the MIC valid.
> + */
> + if (strip_mic)
> + rxs->flag |= RX_FLAG_MMIC_STRIPPED;
> + else if (is_mc && mic_error)
mic_error is always false here. I believe you wanted to set it
based on MIC failure in rx status and may be missed out...
> + rxs->flag |= RX_FLAG_MMIC_ERROR;
> +
> return true;
> }
>
> @@ -1938,6 +1937,9 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
> sc->rx.rxotherant = 0;
> }
>
> + if (rxs->flag & RX_FLAG_MMIC_STRIPPED)
> + skb_trim(skb, skb->len - 8);
> +
> spin_lock_irqsave(&sc->sc_pm_lock, flags);
>
> if ((sc->ps_flags & (PS_WAIT_FOR_BEACON |
> --
> 1.7.3.2
>
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